In conventional fabrics, thread convolutions are formed by binding warp threads and weft threads, said convolutions causing a non-ideally elongated alignment of the threads when used in composite materials. Reinforcing threads used for reinforcing the composite material are therefore kinked or convoluted. This is a problem in so far as the reinforcing threads display their optimal strength properties and/or stiffness properties only if they are arranged as elongated as possible and convolutions and kinks having small radii are avoided, such radii occurring in conventional fabrics between the warp and weft threads in the region of the binding points. It is possible to minimize convolutions of reinforcing threads in conjunction with this in cases when greater distances are provided between the binding points, i.e., when larger floats are planned. This also increases the drapability of the fabric when it needs to be adapted to the three-dimensional shape of the composite material body. However, with larger floats, undesirable shifts of the reinforcing threads may occur so that, when draping the fabric to shape the composite material body, sites of inadequate reinforcement may form and/or the thread density at other sites may be too high.
Frequently, difficulties may also arise when the conventional fabrics are used in so-called preforms during production. One or several fabric layers are superimposed in such preforms in order to later—during a subsequent process step—produce the desired composite material body in a component form. Inasmuch as the dwell time of the component form should be kept as short as possible, one or more preforms are frequently made before the final production of the composite material body, which preforms may then be combined in the component form to produce a composite material body within a shorter period of time. The preform is preformed in a manner such that, when the preform is placed in the component form, only smaller and less time-consuming customization operations are required. Consequently, it is necessary that the fabric of the preform can be brought into a three-dimensional shape that subsequently must be customizable at least in some areas. To accomplish this, binders have been used until now, these being sprays, powders of fleece layers that are laminated or sprayed onto the fabric in order to ensure the dimensional stability of the preform and, at the same time, maintain the drapability of the fabric for continued processing. However, frequently this cannot be accomplished in a reproducible manner, and either the dimensional stability of the preform suffers or the drapability of the preform during continued processing to produce the composite material body suffers.
A fabric for composite material bodies is known from publication U.S. Pat. No. 4,320,160. This fabric comprises a reinforcing system of reinforcing threads and binding threads that are disposed for binding the reinforcing system. As binding threads, either the binding warp threads are interlaced with the binding weft threads by simple binding, or the binding warp threads are interlaced with the reinforcing warp threads or with the reinforcing weft threads of the reinforcing system.
The fabric known from publication U.S. Pat. No. 4,320,160 has the disadvantage that, due to the suggested binding systems, the thread tension of the binding threads affects an undesirable convolution of the reinforcing threads of the reinforcing system. This means that the thread convolution of the reinforcing threads can be prevented only if the thread tension of the binding threads is low. However, the result of this is that it is not possible to ensure sufficient displacement resistance of the reinforcing threads of the reinforcing system, which is of disadvantage when the fabric is to be draped at the time of manufacture of the composite material body. If the desired displacement resistance is to be achieved, the thread tension causes a convolution of the reinforcing threads on the one hand, and, on the other hand there is the risk that the reinforcing yarns are bundled due to the high thread tension of the binding thread between the binding points and that, as a result of this, an undesirable lattice structure with excessively large thread distances between the reinforcing threads is created.
Also, publication DE 20 2005 014 801 U1 discloses a fabric with a reinforcing system of reinforcing threads and binding threads for binding the reinforcing system. Also in this case the binding threads and the reinforcing threads are interlaced, thus bringing about the disadvantages described in conjunction with publication U.S. Pat. No. 4,320,160.